1. Field of the Invention
This invention relates to a reflection density measuring system in which light is projected onto a surface whose reflection density is to be measured and reflected light from the surface is received by a photodetector, whereby the reflection density of the surface is measured.
2. Description of the Prior Art
There has been put into practice a dry-type chemical assay slide for quantitative analysis of a particular component contained in a droplet of a sample liquid such as blood or urine. See Japanese Patent Publication No. 53(1978)-21677, Japanese Unexamined Patent Publication No. 55(1980)-164356 or the like.
When analyzing chemical components in a sample liquid using such a chemical assay slide, a droplet of the sample liquid is deposited on the slide and is held at a constant temperature for a predetermined time in an incubator to permit coloring reaction, and the optical density of the color formed by the coloring reaction is optically measured. That is, measuring light containing a wavelength selected in advance according to the combination of the component to be measured in the sample liquid and the reagent contained in the reagent layer of the slide is projected onto the chemical assay slide and the optical density of the reflected light is measured. Then the content of the component to be measured is quantified on the basis of the optical density of the reflected light by colorimetry.
The optical density of the reflected light is measured by a reflection density measuring system. The reflection density measuring system generally comprises an incubator for receiving the chemical assay slide, and a measuring head which can be opposed to the surface-to-be-measured of the slide in the incubator. After the chemical assay slide is incubated in the incubator, the measuring head is opposed to the surface-to-be-measured of the slide and light is projected onto the surface-to-be-measured by the head and reflected light from the surface-to-be-measured is received by a photosensor in the head.
In medical facilities, laboratories and the like where numerous samples are analized, it is preferred that the reflection densities of a plurality of samples can be sequentially measured, and accordingly there have been proposed various systems for sequentially effecting measurement of reflection densities of a plurality of samples.
For example, in the system disclosed in Japanese Unexamined Patent Publication No. 56(1981)-77746, a plurality of chemical assay slides are sandwiched between a pair of rotatable disks spaced from each other at regular intervals in the circumferential direction of the disks and held at a constant temperature by an incubating heater means provided on the disks, and after incubation for a predetermined time interval, the disks are rotated to successively bring the chemical assay slides into alignment with a measuring head disposed below the disks. Then irradiation light is projected onto each chemical assay slide by the measuring head through an opening formed in the lower disk and reflected light is detected by a photosensor. However, the system is disadvantageous in that complicated and cumbersome rotating system and controlling systems are necessary for rotating the large and heavy disks, thereby adding to the overall size of the system and manufacturing cost.